
package geym.conc.ch2.notsafe;

import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Map;

/**
 * use JDK 7
 * JDK 8不会死循环，只会数据不一致
 *
 * @author Geym
 */
public class JDK8HashMapMultiThread {

    static Map<String, String> map = new HashMap<String, String>();
//    static Map map = new ConcurrentHashMap(10);

    public static class AddThread implements Runnable {
        int start = 0;

        public AddThread(int start) {
            this.start = start;
        }

        @Override
        public void run() {
            for (int i = start; i < 10000; i++) {
                map.put(Integer.toString(i), Integer.toString(i));
            }
        }
    }

    public static void test() throws Exception {
        Thread t1 = new Thread(new JDK8HashMapMultiThread.AddThread(0));
        Thread t2 = new Thread(new JDK8HashMapMultiThread.AddThread(1));
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println("map size=" + map.size());
        System.out.println("table count=" + getTableSize());
    }

    public static void main(String[] args) throws Exception {

        for (int i = 0; i < 100; i++) {
            test();
            map = new HashMap<String, String>();
        }
    }

    public static int getTableSize() throws Exception {
        Field fTable = map.getClass().getDeclaredField("table");
        fTable.setAccessible(true);
        Object[] table = (Object[]) fTable.get(map);
        int count = 0;
        for (int i = 0; i < table.length; i++) {
            if (table[i] != null) count++;
        }
        fTable.setAccessible(false);
        return count;
    }

}
